ADORA2A and Huntington disease: Because the glutamate release was dynamically altered from an enhancement at the presymptomatic stage to a decrease at the symptomatic stage during disease progression of HD mice [49], and since local glutamate level was recently shown to dictate the effect of A2AR on neuronal death in an animal model of traumatic brain injury [52], it is possible that the stage of disease progression might contribute to the complex role of A2AR in HD.